/*
 * Copyright 2002-2021 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.mvc.condition;

import org.springframework.lang.Nullable;
import org.springframework.util.AntPathMatcher;
import org.springframework.util.ObjectUtils;
import org.springframework.util.PathMatcher;
import org.springframework.util.StringUtils;
import org.springframework.web.util.UrlPathHelper;
import org.springframework.web.util.pattern.PathPattern;

import javax.servlet.http.HttpServletRequest;
import java.util.*;

/**
 * A logical disjunction (' || ') request condition that matches a request
 * against a set of URL path patterns.
 *
 * <p>In contrast to {@link PathPatternsRequestCondition} which uses parsed
 * {@link PathPattern}s, this condition does String pattern matching via
 * {@link org.springframework.util.AntPathMatcher AntPathMatcher}.
 *
 * @author Rossen Stoyanchev
 * @since 3.1
 */
public class PatternsRequestCondition extends AbstractRequestCondition<PatternsRequestCondition> {

    private final static Set<String> EMPTY_PATH_PATTERN = Collections.singleton("");


    private final Set<String> patterns;

    private final PathMatcher pathMatcher;

    private final boolean useSuffixPatternMatch;

    private final boolean useTrailingSlashMatch;

    private final List<String> fileExtensions = new ArrayList<>();


    /**
     * Constructor with URL patterns which are prepended with "/" if necessary.
     *
     * @param patterns 0 or more URL patterns; no patterns results in an empty
     *                 path {@code ""} mapping which matches all requests.
     */
    public PatternsRequestCondition(String... patterns) {
        this(patterns, true, null);
    }

    /**
     * Variant of {@link #PatternsRequestCondition(String...)} with a
     * {@link PathMatcher} and flag for matching trailing slashes.
     *
     * @since 5.3
     */
    public PatternsRequestCondition(String[] patterns, boolean useTrailingSlashMatch,
                                    @Nullable PathMatcher pathMatcher) {

        this(patterns, null, pathMatcher, useTrailingSlashMatch);
    }

    /**
     * Variant of {@link #PatternsRequestCondition(String...)} with a
     * {@link UrlPathHelper} and a {@link PathMatcher}, and whether to match
     * trailing slashes.
     * <p>As of 5.3 the path is obtained through the static method
     * {@link UrlPathHelper#getResolvedLookupPath} and a {@code UrlPathHelper}
     * does not need to be passed in.
     *
     * @since 5.2.4
     * @deprecated as of 5.3 in favor of
     * {@link #PatternsRequestCondition(String[], boolean, PathMatcher)}.
     */
    @Deprecated
    public PatternsRequestCondition(String[] patterns, @Nullable UrlPathHelper urlPathHelper,
                                    @Nullable PathMatcher pathMatcher, boolean useTrailingSlashMatch) {

        this(patterns, urlPathHelper, pathMatcher, false, useTrailingSlashMatch);
    }

    /**
     * Variant of {@link #PatternsRequestCondition(String...)} with a
     * {@link UrlPathHelper} and a {@link PathMatcher}, and flags for matching
     * with suffixes and trailing slashes.
     * <p>As of 5.3 the path is obtained through the static method
     * {@link UrlPathHelper#getResolvedLookupPath} and a {@code UrlPathHelper}
     * does not need to be passed in.
     *
     * @deprecated as of 5.2.4. See class-level note in
     * {@link org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping}
     * on the deprecation of path extension config options.
     */
    @Deprecated
    public PatternsRequestCondition(String[] patterns, @Nullable UrlPathHelper urlPathHelper,
                                    @Nullable PathMatcher pathMatcher, boolean useSuffixPatternMatch,
                                    boolean useTrailingSlashMatch) {

        this(patterns, urlPathHelper, pathMatcher, useSuffixPatternMatch, useTrailingSlashMatch, null);
    }

    /**
     * Variant of {@link #PatternsRequestCondition(String...)} with a
     * {@link UrlPathHelper} and a {@link PathMatcher}, and flags for matching
     * with suffixes and trailing slashes, along with specific extensions.
     * <p>As of 5.3 the path is obtained through the static method
     * {@link UrlPathHelper#getResolvedLookupPath} and a {@code UrlPathHelper}
     * does not need to be passed in.
     *
     * @deprecated as of 5.2.4. See class-level note in
     * {@link org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping}
     * on the deprecation of path extension config options.
     */
    @Deprecated
    public PatternsRequestCondition(String[] patterns, @Nullable UrlPathHelper urlPathHelper,
                                    @Nullable PathMatcher pathMatcher, boolean useSuffixPatternMatch,
                                    boolean useTrailingSlashMatch, @Nullable List<String> fileExtensions) {

        // 拼接上 '/' 开头
        this.patterns = initPatterns(patterns);
        // 路径匹配
        this.pathMatcher = pathMatcher != null ? pathMatcher : new AntPathMatcher();
        this.useSuffixPatternMatch = useSuffixPatternMatch;
        this.useTrailingSlashMatch = useTrailingSlashMatch;

        if (fileExtensions != null) {
            for (String fileExtension : fileExtensions) {
                if (fileExtension.charAt(0) != '.') {
                    fileExtension = "." + fileExtension;
                }
                this.fileExtensions.add(fileExtension);
            }
        }
    }

    private static Set<String> initPatterns(String[] patterns) {
        if (!hasPattern(patterns)) {
            return EMPTY_PATH_PATTERN;
        }
        Set<String> result = new LinkedHashSet<>(patterns.length);
        for (String pattern : patterns) {
            if (StringUtils.hasLength(pattern) && !pattern.startsWith("/")) {
                pattern = "/" + pattern;
            }
            result.add(pattern);
        }
        return result;
    }

    private static boolean hasPattern(String[] patterns) {
        if (!ObjectUtils.isEmpty(patterns)) {
            for (String pattern : patterns) {
                if (StringUtils.hasText(pattern)) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Private constructor for use when combining and matching.
     */
    private PatternsRequestCondition(Set<String> patterns, PatternsRequestCondition other) {
        this.patterns = patterns;
        this.pathMatcher = other.pathMatcher;
        this.useSuffixPatternMatch = other.useSuffixPatternMatch;
        this.useTrailingSlashMatch = other.useTrailingSlashMatch;
        this.fileExtensions.addAll(other.fileExtensions);
    }


    public Set<String> getPatterns() {
        return this.patterns;
    }

    @Override
    protected Collection<String> getContent() {
        return this.patterns;
    }

    @Override
    protected String getToStringInfix() {
        return " || ";
    }

    /**
     * Whether the condition is the "" (empty path) mapping.
     */
    public boolean isEmptyPathMapping() {
        return this.patterns == EMPTY_PATH_PATTERN;
    }

    /**
     * Return the mapping paths that are not patterns.
     *
     * @since 5.3
     */
    public Set<String> getDirectPaths() {
        if (isEmptyPathMapping()) {
            return EMPTY_PATH_PATTERN;
        }
        Set<String> result = Collections.emptySet();
        for (String pattern : this.patterns) {
            // 不匹配通配符的才算是直接的路径，比如 [/*,/index]
            if (!this.pathMatcher.isPattern(pattern)) {
                result = (result.isEmpty() ? new HashSet<>(1) : result);
                // /index
                result.add(pattern);
            }
        }
        return result;
    }

    /**
     * Returns a new instance with URL patterns from the current instance ("this") and
     * the "other" instance as follows:
     * <ul>
     * <li>If there are patterns in both instances, combine the patterns in "this" with
     * the patterns in "other" using {@link PathMatcher#combine(String, String)}.
     * <li>If only one instance has patterns, use them.
     * <li>If neither instance has patterns, use an empty String (i.e. "").
     * </ul>
     */
    @Override
    public PatternsRequestCondition combine(PatternsRequestCondition other) {
        if (isEmptyPathMapping() && other.isEmptyPathMapping()) {
            return this;
        } else if (other.isEmptyPathMapping()) {
            return this;
        } else if (isEmptyPathMapping()) {
            return other;
        }
        Set<String> result = new LinkedHashSet<>();
        if (!this.patterns.isEmpty() && !other.patterns.isEmpty()) {
            for (String pattern1 : this.patterns) {
                for (String pattern2 : other.patterns) {
                    result.add(this.pathMatcher.combine(pattern1, pattern2));
                }
            }
        }
        return new PatternsRequestCondition(result, this);
    }

    /**
     * Checks if any of the patterns match the given request and returns an instance
     * that is guaranteed to contain matching patterns, sorted via
     * {@link PathMatcher#getPatternComparator(String)}.
     * <p>A matching pattern is obtained by making checks in the following order:
     * <ul>
     * <li>Direct match
     * <li>Pattern match with ".*" appended if the pattern doesn't already contain a "."
     * <li>Pattern match
     * <li>Pattern match with "/" appended if the pattern doesn't already end in "/"
     * </ul>
     *
     * @param request the current request
     * @return the same instance if the condition contains no patterns;
     * or a new condition with sorted matching patterns;
     * or {@code null} if no patterns match.
     */
    @Override
    @Nullable
    public PatternsRequestCondition getMatchingCondition(HttpServletRequest request) {
        String lookupPath = UrlPathHelper.getResolvedLookupPath(request);
        List<String> matches = getMatchingPatterns(lookupPath);
        return !matches.isEmpty() ? new PatternsRequestCondition(new LinkedHashSet<>(matches), this) : null;
    }

    /**
     * Find the patterns matching the given lookup path. Invoking this method should
     * yield results equivalent to those of calling {@link #getMatchingCondition}.
     * This method is provided as an alternative to be used if no request is available
     * (e.g. introspection, tooling, etc).
     *
     * @param lookupPath the lookup path to match to existing patterns
     * @return a collection of matching patterns sorted with the closest match at the top
     */
    public List<String> getMatchingPatterns(String lookupPath) {
        List<String> matches = null;
        for (String pattern : this.patterns) {
            // 匹配
            String match = getMatchingPattern(pattern, lookupPath);
            if (match != null) {
                matches = (matches != null ? matches : new ArrayList<>());
                matches.add(match);
            }
        }
        if (matches == null) {
            return Collections.emptyList();
        }
        if (matches.size() > 1) {
            // 对结果排序
            matches.sort(this.pathMatcher.getPatternComparator(lookupPath));
        }
        return matches;
    }

    @Nullable
    private String getMatchingPattern(String pattern, String lookupPath) {
        // 等值匹配
        if (pattern.equals(lookupPath)) {
            return pattern;
        }
        // 使用后缀匹配
        if (this.useSuffixPatternMatch) {
            // 存在文件扩展名
            if (!this.fileExtensions.isEmpty() && lookupPath.indexOf('.') != -1) {
                for (String extension : this.fileExtensions) {
                    // 拼接上文件扩展名在进行屁屁
                    if (this.pathMatcher.match(pattern + extension, lookupPath)) {
                        return pattern + extension;
                    }
                }
            } else {
                // 有后缀
                boolean hasSuffix = pattern.indexOf('.') != -1;
                // 没有后缀，拼接上后缀进行匹配
                if (!hasSuffix && this.pathMatcher.match(pattern + ".*", lookupPath)) {
                    return pattern + ".*";
                }
            }
        }
        // 匹配
        if (this.pathMatcher.match(pattern, lookupPath)) {
            return pattern;
        }
        // 尾部拼接上 / 进行匹配
        if (this.useTrailingSlashMatch) {
            if (!pattern.endsWith("/") && this.pathMatcher.match(pattern + "/", lookupPath)) {
                return pattern + "/";
            }
        }
        return null;
    }

    /**
     * Compare the two conditions based on the URL patterns they contain.
     * Patterns are compared one at a time, from top to bottom via
     * {@link PathMatcher#getPatternComparator(String)}. If all compared
     * patterns match equally, but one instance has more patterns, it is
     * considered a closer match.
     * <p>It is assumed that both instances have been obtained via
     * {@link #getMatchingCondition(HttpServletRequest)} to ensure they
     * contain only patterns that match the request and are sorted with
     * the best matches on top.
     */
    @Override
    public int compareTo(PatternsRequestCondition other, HttpServletRequest request) {
        String lookupPath = UrlPathHelper.getResolvedLookupPath(request);
        Comparator<String> patternComparator = this.pathMatcher.getPatternComparator(lookupPath);
        Iterator<String> iterator = this.patterns.iterator();
        Iterator<String> iteratorOther = other.patterns.iterator();
        while (iterator.hasNext() && iteratorOther.hasNext()) {
            int result = patternComparator.compare(iterator.next(), iteratorOther.next());
            if (result != 0) {
                return result;
            }
        }
        if (iterator.hasNext()) {
            return -1;
        } else if (iteratorOther.hasNext()) {
            return 1;
        } else {
            return 0;
        }
    }

}
